This invention relates to the formation of tubular conductors which consist of a niobium layer and a layer of normal conducting metal in general, and more particularly to an improved method of forming such tubular conductors.
A method for manufacturing such tubular conductors is disclosed in U.S. Pat. No. 3,777,368 issued Dec. 11, 1973 and assigned to the same assignee as the present invention. In the method disclosed therein, a ribbon consisting of layers of niobium and a normally conducting metal and which has at its edges a niobium flange is first fabricated. The ribbon is then bent to form a tube in such a manner that the niobium flanges at both edges of the ribbons abut and subsequently the niobium flanges are joined together, preferably by electron beam welding. Specifically, as disclosed in the above referenced patent, the fabrication of the ribbon consisting of the two layers is accomplished by first welding, to the two edges of a ribbon shaped niobium foil, niobium flanges, using electron beam welding to form a U-shaped niobium cross section. The empty space of the U-shaped cross section is then at least partially filled with a normal conducting metal. After this, the normally conducting metal is joined to the niobium ribbon and niobium flanges by the application of heat. An alternate method of fabrication also disclosed in the above reference patent comprises first joining the lateral edges of a copper ribbon to niobium flanges using diffusion and then applying a niobium layer on at least one side of the ribbon consisting of the niobium flanges and copper ribbons. As disclosed, the niobium layer can be applied by means of fusion electrolysis.
Although the methods disclosed in the above referenced patent are satisfactory, they require many steps and are not particularly simple. Thus, it is the object of this invention to provide a simpler method of forming tubular conductors of this nature.